1. Technical Field
The present invention relates in general to electronic systems and, in particular, to power management in electronic systems. Still more particularly, the present invention relates to power sequencing in an electronic system such as a data processing system.
2. Description of the Related Art
In many electronic systems such as computer systems, the integrated circuit components of the system are mounted on circuit cards. Such circuit cards typically have multiple layers, including one or more interconnect layers that interconnect pins of the various integrated circuits and one or more power and ground planes that supply operating voltages to the integrated circuits. Multiple power planes are often included within a circuit card in order to provide multiple different supply voltages, for example, 1.8 V, 3.3 V, and 5 V, that satisfy the power requirements of the integrated circuits mounted on the circuit card.
In order to power up the integrated circuit components mounted on a multiple-power-plane circuit card in a coherent manner, it is commonly required to sequence the supply of power to the power planes in a particular order. The order in which power is applied to the power planes, which is typically controlled by a power control circuit mounted on the circuit card, may vary between circuit cards, depending on the integrated circuit technologies represented on each circuit card.
A problem arises in that it may be desirable after a circuit card has been installed in an electronic system to modify the default power supply sequencing hardwired into the circuit card's power control circuit. For example, if the circuit card includes a socket for a processor chip, it may be necessary to alter the power sequencing of the circuit card in order to support an upgrade of the processor to one fabricated utilizing a new, faster integrated circuit technology.
As should thus be apparent, it would be useful and desirable to provide a method and system for power sequencing in an electronic system that permit the default power sequencing of a circuit card to be easily modified.